"Did David, son of this David Porter go to England?"
Yes, I think he did and married Mary Hannah Banham. I followed this David up, thinking he was my David also born 1876 but to different parents - Robert Porter and Ann(ie) Dixon / Dickson. What is puzzling me is that I can't find a birth entry in the online GRONI index for that year for any other David apart from mine.
You also mention Seagoe Porters going to Scotland. I may be able to help with that. What names/dates are they?